The brightness of a projection display system is related to the minimum of the system étendue and the étendue of the light source used in the system. Therefore, when a mismatch between the system étendue and the source étendue occurs, the optical efficiency of the system is suboptimal.
Generally, the cost and size of optical components impose limitations on the increase of the system étendue of a particular projection display system. On the other hand, the source étendue is related to the surface area and emission pattern of the light source.
However, once the source étendue exceeds the system étendue, negligible benefits in terms of brightness can be achieved by increasing the surface area of the light source. To further increase the brightness of the system, the optical flux of the light source would need to be increased (for example, increasing the temperature of an incandescent light bulb), which results in a more expensive display system.
Therefore, methods and systems that enable improved brightness in projection display systems without suffering from the above described limitations are needed.